Cathode for electrodeposition



Aug. 20, 1935. J. YOUNG 2,011,885

CATHODE FOR ELECTRODEPOSITION Filed July 25, 1934 INVENTOR v M 13.ORNEYS Patented Aug. 2%, i935 UNETED sr r s Parent @FHGE CATHODE FOBELECTRODEPOSITION Maryland Application July 23, 1934, Serial No. 736,5313' Claims. (01. 204-6) This invention relates to the electro-depositionof sheet metal, and consists. in cathode structure. The object in viewis such control of deposit at the edge of the stripping surface as toavoid damage to the deposited sheet when being stripped from thecathode.

In the accompanying drawing Fig. I is a fragmentary view in section of acathode in which the invention is embodied; Fig. II is a similar viewillustrating a modification in detail; and Fig. 111 is a similar view inwhich to the showing of Fig. I a structural feature is added that adaptsthe cathode to particular conditions of service.

Referring first to Fig. I, the essentialpart of a cathode of practicalform is shown, consisting of or including a supporting body 5, that maybe understood to be a sheet of metal (iron or copper),- and a sheet 2 ofsuitable metal (chrome steel, for example), borne by and facing the bodyI, whose exposed surface is the stripping surface.

Ordinarily the current for carrying on the operation of electrolysiswill be supplied through it. The two bodies I and 2 may extend inplanes,

or they may (and ordinarily will be of cylindrical shape, the sheet 2surrounding the supporting sheet I.

It manifestly is desirable that the electrolytic deposit be limited tothe stripping surface of sheet 2, and the proposal to that end has beenmade to set a band of insulating material (of such material, forexample, as that phenolic resin known as bakelite) along the edges ofthe stripping surface- This proposal has, however, been foundinadequate. It hasbeen found impossible under practical operatingconditions to provide such a limiting band of insulation and not have aseam the sheet,--a seam into which the electrolyte -will penetrate. Uponthe metal wall of that seamthere will be an electrolytic deposit of suchmass and so intimately united with the wall of metal that, whenafterward the finished electro-deposited sheet is being stripped .fromthe cathode,

this unintended and undesired deposit in the seam wfll interfere withthe stripping operation and will tend to cause breakageof the depositedsheet along its edges.

, In Fig. I of the. drawing a limiting band 3 of insulating material isshown abutting the edge of-sheet 2, and it is in the seam between themeeting surfaces of these two bodies that (lacking further preventiveprovision) the undesired and prejudicial deposit occurs.

The invention lies in the discovery that if to the assembly of sheet 2and band 3 a second band 4 of conducting material be addeda band thatshall overlie the seam specified, and that shall make contact with theface of sheet 2 at the margin thereof and that shall itself be includedin the electrolytic current--the band 4 will steal away the current thatotherwise would flow through the electrolyte and to the metal wall ofthe seam, and that .there will be no appreciable deposit on that wall.The electrolyte will penetrate: that is practically inevitable. But thebody of electrolyte that so penetrates will, in consequence of thepresence of the band 4, be so far relieved of current flow that noappreciable or significant electrolytic action will there occur. Itfollows that a serious practical difficulty in cathode structure iscorrected and overcome, and thestripping cathode for the forming ofsheet metal electrolytically is rendered notably more effective andpracticable. I

In Fig. I I have indicated diagrammatically a conductor 9 for theelectrolytic current, and have shown the band 4 to be included incircuit with the bodies l and 2;

Necessarily the band 4, becoming in the manner described inefiect partof the cathode, will itself be. coated with an-electrolytic deposit, butin the stripping of the deposited sheet from the cathode there will be aline of weakness following the angle formed by and between the strippingsurface of sheet 2 and the band 4, along which line the marginal depositwill break away, leaving the desired sheet entire. There will, however,be waste, in that the deposit formed over the surfaces of band 4 will beundesired and futile. Accordingly, the band may advantageously bemodified, and formed as shown in Fig. 11. Here the band 5 is formed ofinsulating material, and faced only with a metallic facstantial degreereach the metallic seam face, and

"inevitably depositedupon the band is limitedto the exposed metalsurfaces,. and they are (as compared withthe structure of Fig. I) ofrelatively small extent.

Figs. I and II show the edge portion of such a 5 cathode as may bearranged to stand vertically in a cell, with one edge of the band 3 andone edge of band! rising above the surface of the electrolyte. Incertain cases the cathode may be submerged, and then further protectionmust be provided for the otherwise exposed portions of body I. Suchfurther protection is indicated in Fig. III by a strip 1' of insulationhaving a facing .8 of metal that is extended around the edge of the bodyI, and overlies both the seam between the sheet 2 and the band 3 (asalready described) and similarly overlies the seam between a secondsheet 2' and a second strip 3' similarly applied to the opposite face ofbody I. case is of plane-surfaced extent, not cylindrical.)

The angle at which the band 4 (6, 8) meets the stripping surface may bea right angle, as in Fig. I it is shown to be, or it may be an obliqueangle, as in Fig. II; and, being oblique, it may, manifestly, be acuteor obtuse and of such degree of obliquity as may be found preferable.

I claim as my invention: 1

1. A stripping cathode for an electrolytic cell including a body ofconducting material provided with a stripping surface, a body ofinsulating material abutting upon the body of conducting material at theedge of such stripping surface, and a band of conducting materialoverlying the seam formed by and between the two bodies aforesaid and incontact with the stripping surface of the body of conducting material atthe margin thereof and presenting a surface adjacent to and angularlydisposed to the adjacent portion of said stripping surface, the saidband adapted to be included with the body of conducting material in thecircuit of the electrolytic current, whereby as operation progresses acontinuous deposit weakened at the angle is formed upon said stripping(The cathode in this surface and upon the adjacent angularly disposedsurface of said band.

2. A stripping cathode for an electrolytic cell including a body-ofconducting material provided with a stripping surface, a body ofinsulating material abutting upon the body of conducting material at theedge of such stripping surface, and a metal-surfaced band of insulatingmaterial overlying the seam formed by and between the two bodiesaforesaid and in contact with the stripping surface of the body ofconducting material at the margin thereof and presenting a conductingsurface adjacent to and angularly disposed to the adjacent portion ofsaid stripping surface, the said band adapted to be included with thebody of conducting material in the circuit of the electrolytic current,whereby as operation progresses a continuous deposit weakened at theangle is formed upon said stripping surface and upon the adjacentangularly disposed surface of said band.

3. A stripping cathode for an electrolytic cell including a body ofconducting material provided with a stripping surface, a body ofinsulating material arranged adjacent the said body of conductingmaterial, and means for preventing substantial electrolytic depositwithin the seam, such means including a band of conducting materialoverlying both the body of conducting material first named and the bodyof insulating material, the said band being included with the said bodyof conducting material in the electrolytic circuit, the arrangementbeing such that access of electrolyte to the seam formed by and betweenthe body of conducting material first named and the body of insulatingmaterial is through the seam formed by and between the body ofconducting material and the overlying band of conducting material.

- JOHN L. YOUNG.

